OVARIES OF FISHES. 161 
degenerate yolked ovum left at the previous spawning. In another 
of the same size the right ovary was 2% inches long, 23 imches from 
Fira. 3.—Ovum of dab in which yolk has just commenced to develop ; magnified 
about 250 times. yk., yolk; g.v., germinal vesicle with nucleoli. In Fig. 2 the 
germinal vesicle is shown in optical section, here in surface view. 
the posterior end of the ventral fin, and was in the same condition. 
These flounders spawned at the end of April and beginning of May, 
and it is seen that the condition of the germinal tissue had almost 
reverted to that of the immature ovary, but the size and appearance 
of the ovary showed that the fish had spawned. Another 
specimen, 122 inches long, from the same tank, was killed on August 
25th ; the germinal tissue exhibited only yolkless ova, all traces of 
previous spawning had disappeared. On August 31st I examined a 
specimen 153 inches long caught in the Hamoaze. The ovary was 
large and flaccid, and had evidently spawned before. The formation 
of yolk in next season’s eggs had just commenced, and no trace of 
the previous spawning was left in the appearance of the germinal 
tissue under the microscope. 
I have not yet been able to examine the spent condition or to 
determine the period at which yolk commences to develop in the 
merry sole (Plewronectes microcephalus). In December and January 
mature specimens were in an advanced condition but not ripe. Ripe 
specimens were obtained from February to July, but none in the spent 
condition, 
Common Sole. 
My observations on the ovary of this species are far from com- 
plete, and I shall hope to resume the discussion of it on a future 
occasion. From what I have hitherto observed I am inclined to 
infer that the development of the yolk in the sole extends 
beyond the period of a year, so that the maturation of one 
